Shaped nonwoven fabric

ABSTRACT

The purpose of the present invention is to provide a porous shaped nonwoven fabric, which has excellent texture and good liquid permeability, is bulky, and is less susceptible to liquid return. The present invention provides a shaped nonwoven fabric with sections of relatively low specific volume and sections of relatively high specific volume present in parallel lines on the surface of the nonwoven fabric, wherein the portion with a low specific volume have thermally compressed areas alternating with porous areas and the portion with a high specific volume have ridges that have not been thermally compressed.

TECHNICAL FIELD

The present invention relates to a shaped nonwoven fabric which is bulky and has pores, and a product using the same.

BACKGROUND ART

Recently, increased comfort of nonwoven fabrics used for sanitary materials such as disposable diapers and sanitary napkins has been demanded, and improvements have been progressing. Particularly, special nonwoven fabrics have come to be used for surface materials in order to reduce stuffiness due to skin rashes, urine, or menstrual blood. In order to reduce a contact area with the skin, nonwoven fabrics that have been subjected to shaping and nonwoven fabrics having pores that increase an absorption speed can be exemplified.

As a conventional nonwoven fabric having pores, a nonwoven fabric in which pores are formed by perforating with a heated pin while sandwiching the nonwoven fabric between a pin roll and a protrusion roll is known (see, for example, Patent Literature 1). However, in this method, since the nonwoven fabric is crushed by the pin roll, there is a problem in that bulkiness of the nonwoven fabric is reduced and a texture deteriorates. Also, since the nonwoven fabric is consolidated except for the pores, there is a problem in that a liquid does not easily pass therethrough, the bulkiness is reduced, and a liquid return is large.

In order to solve these problems, a shaped nonwoven fabric in which perforating and shaping are performed with a perforating device in which a protrusion roll and a perforating pin roll are combined has been studied (see, for example, Patent Literature 2). However, since a portion of the shaping involves compression with the protrusion roll, there is a problem in that a liquid does not easily pass therethrough. Also, since a shape retention property is low due to tension (a tensile force) of the nonwoven fabric, the shaped portion may break or the like during processing of disposable diapers and sanitary napkins, and thus there is a problem in that the shape retention property deteriorates.

CITATION LIST Patent Literature [Patent Literature 1]

Japanese Unexamined Patent Application Publication No. H06-330443

[Patent Literature 2]

Japanese Unexamined Patent Application Publication No. 2009-215667

SUMMARY OF INVENTION Technical Problem

From the foregoing, it is an objective of the present invention to provide a shaped nonwoven fabric having pores which is excellent in texture, satisfactory in liquid permeability, bulky, and improved in liquid return.

Solution to Problem

The present inventors have conducted intensive research to solve these problems. As a result, they have found that the above-described problems can be solved by making a nonwoven fabric such that a portion with a relatively low specific volume and a portion with a relatively high specific volume are each linearly present on a surface of the nonwoven fabric and pores are present on the portion with a low specific volume, and thus completed of the present invention.

The present invention has the following configurations.

[1] A shaped nonwoven fabric in which a portion with a relatively low specific volume and a portion with a relatively high specific volume are respectively linearly present in parallel on a surface of the nonwoven fabric, wherein the portion with a low specific volume alternately includes a thermally compressed part and a porous part, and the portion with a high specific volume includes a ridge that is not thermally compressed. [2] The shaped nonwoven fabric of [1], in which, in a nonwoven fabric cross section of the portion with a relatively high specific volume on a surface of the nonwoven fabric, a low specific volume region is provided at a center of the nonwoven fabric cross section. [3] The shaped nonwoven fabric of [1], in which, in a nonwoven fabric cross section of the portion with a relatively high specific volume on a surface of the nonwoven fabric, a high specific volume region is provided at a center of the nonwoven fabric cross section. [4] The shaped nonwoven fabric according to any one of the above-described [1] to [3], in which a specific volume ratio defined by the following expression is 5% or more and less than 50%.

Specific volume ratio=specific volume at portion with low specific volume/specific volume at portion with high specific volume×100 (%)

Advantageous Effects of Invention

The shaped nonwoven fabric of the present invention is bulky and excellent in texture. Further, since the portion with a relatively high specific volume includes the ridge that is not thermally compressed and the portion with a relatively low specific volume alternately includes a thermally compressed part and a porous part, liquid permeability is satisfactory because a liquid passage time of a liquid is short (absorption speed is high), liquid returnability is reduced because it is bulky, and thereby the shaped nonwoven fabric of the present invention has satisfactory properties.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an image of a cross-sectional view of a nonwoven fabric showing one embodiment of a shaped nonwoven fabric of the present invention.

FIG. 2 is an image of a cross-sectional view of a nonwoven fabric showing one embodiment of the shaped nonwoven fabric of the present invention.

FIG. 3 is an image of the shaped nonwoven fabric of the present invention when viewed from above.

FIG. 4 is a schematic view of a pair of thermal compression shaping rolls used in the present invention when viewed from the front.

FIG. 5 is a schematic view showing a low specific volume region (5) provided at a center of a nonwoven fabric cross section in the nonwoven fabric cross section of a portion with a relatively high specific volume of the shaped nonwoven fabric of the present invention.

FIG. 6 is a schematic view showing a high specific volume region (6) provided at a center of a nonwoven fabric cross section in the nonwoven fabric cross section of the portion with a relatively high specific volume of the shaped nonwoven fabric of the present invention.

DESCRIPTION OF EMBODIMENTS

A shaped nonwoven fabric of the present invention is a shaped nonwoven fabric in which a portion with a relatively low specific volume and a portion with a relatively high specific volume are linearly present in parallel respectively on a surface of the nonwoven fabric, wherein the portion with a low specific volume alternately includes a thermally compressed part and a porous part, and the portion with a high specific volume includes a ridge that is not thermally compressed.

In order to obtain a nonwoven fabric having such a structure, for example, a nonwoven fabric made of heat-fusible composite fibers may be processed using a thermocompression type pin roller.

In the shaped nonwoven fabric of the present invention, a specific volume ratio defined by the following expression is preferably 5% or more and less than 50%.

Specific volume ratio=specific volume at portion with low specific volume/specific volume at portion with high specific volume×100 (%)

Even among nonwoven fabrics having the same thickness, it is excellent in absorbency when a nonwoven fabric has the specific volume ratio in a range of 5% or more and less than 50% . The specific volume ratio is more preferably 5% or more and 45% or less, and still more preferably 10% or more and 40% or less in terms of bulkiness.

As the nonwoven fabric used in the present invention, a nonwoven fabric made of heat-fusible composite fibers obtained by thermally adhering a web obtained by a card method using a circulation type hot-air dryer can be preferably used.

Also, as the heat-fusible composite fibers, a composite fiber in which polyethylene (PE) such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), or high-density polyethylene (HDPE), polypropylene (PP) such as crystalline polypropylene, or a copolymer (Co-PP) of propylene and ethylene or α-olefin in which propylene as the main component, and polyester (PET) such as polyethylene terephthalate, polybutylene terephthalate, or a polyester copolymer (Co-PET) are combined can be used. As the specific combinations, PP/PE, PP/Co-PP, PET/PE, PET/LLDPE, and PET/Co-PET can be exemplified. Also, as types of the composite fiber, a sheath-core type, a parallel type, an eccentric sheath-core type, or the like can be exemplified.

A denier of the heat-fusible composite fiber used in the present invention is preferably 0.8 dtex to 20 dtex, and more preferably 1.0 dtex to 10 dtex. Particularly, when the denier of the heat-fusible composite fiber forming a nonwoven fabric used for a surface layer (on a side touching the skin) is made finer, since flexibility and texture of the nonwoven fabric are satisfactory, and furthermore, smoothness is improved, effects of reducing friction with the skin and reducing rashes are enhanced. However, the nonwoven fabric formed of the heat-fusible composite fibers having a fine denier has a problem in that a liquid does not easily pass therethrough due to the increased number of fibers forming the nonwoven fabric. Therefore, in the present invention, although the nonwoven fabric is perforated at regular intervals to maintain liquid permeability, it is preferable to use a product of fiber denier within the present range when a balance between the liquid permeability and texture, and productivity in processing are considered.

When the nonwoven fabric is a single layer, a basis weight of the nonwoven fabric is preferably 10 g/m² to 100 g/m², and more preferably 15 g/m² to 70 g/m². When the basis weight is within the above-described range, bulkiness or absorption performance of the nonwoven fabric is satisfactory. Also, when the nonwoven fabric is multiple layers, a total basis weight of the multiple layers is preferably 10 g/m² to 100 g/m², and more preferably 15 g/m² to 70 g/m².

A width of the portion with a relatively high specific volume that is present linearly (also referred to as a convex portion or a ridge), that is, a width of the convex portion in a CD direction, is not particularly limited, but the width is preferably 2 mm or more and 10 mm or less, and more preferably 3 mm or more and 6 mm or less. When the width is 2 mm or more, a sufficient ridge can be formed, and the effects of the present invention can be sufficiently obtained. Also, when the width is 10 mm or less, since a contact area with the skin does not become too large, the effects of the present invention can be sufficiently obtained.

A width of the portion with a relatively low specific volume that is present linearly (also referred to as a concave portion), that is, a width of the concave portion in the CD direction, is not particularly limited, but the width is preferably 1 mm or more and 10 mm or less, and more preferably 2 mm or more and 6 mm or less. When the concave portion is 1 mm or more, the concave portion can be formed, and it is preferable when the width of the concave portion is 10 mm or less because a consolidated portion does not become too large and liquid absorption is not inhibited.

As long as the widths of the convex portion and the concave portion are within the above-described ranges, the widths of the convex portion and the concave portion do not have to be constant. Also, when the convex portion and the concave portion are disposed substantially on a straight line, a shape of a boundary line of the convex portion and the concave portion such as a wave pattern or a jagged pattern is not particularly limited.

A diameter of a pore of the porous part of the concave portion may be, for example, preferably 0.5 mm to 5 mm in a case that the pore is substantially circular. Also, the pores are preferably separated by a distance of 1 mm or more and 10 mm or less. With the range described above, a balance between a liquid passage time and a liquid return amount is satisfactory. As the diameter of the pore decreases and the distance between the pores increases, the liquid passage time becomes longer while the liquid return amount becomes smaller, and on the other hand, as the diameter of the pore increases and the distance between the pores decreases, the liquid return amount becomes larger while the liquid passage time becomes shorter. Also, when the distance is too large, the liquid passage time tends to be long.

The shaped nonwoven fabric of the present invention can be manufactured using a nonwoven fabric obtained by a circulation type hot-air dryer of a card method as a row material by performing perforating and shaping processing thereon using a thermal compression shaping roll (see FIG. 4; upper and lower temperature of the roll being 115° C.) constituted by an upper thermal roll in which a protruding portion (pin roll) that enables compression perforating and a portion that is recessed so that a thickness of the nonwoven fabric is left are included alternately in a width direction of the roll, and a lower thermal roll having pores open at portions receiving the pin roll.

In the shaped nonwoven fabric of the present invention, a surface to be used is not particularly limited, but when it is used as a surface material for sanitary materials such as disposable diapers and sanitary napkins, it is preferable to make a net surface an upper layer because there is a problem of rashes on a surface that touches the skin due to fluff generated by raised hairs of the nonwoven fabric.

The shaped nonwoven fabric of the present invention may further be shaped by laminating it into an upper and lower two-layered nonwoven fabric made of the heat-fusible composite fibers and providing communicating holes in a longitudinal direction thereof. The manufacturing method is not particularly limited as long as such communicating holes can be obtained. For example, when a space (hollow portion) or a density difference (specific volume difference) is formed by laminating the upper layer and the lower layer, a cushioning property of the nonwoven fabric is increased, and the nonwoven fabric becomes bulky with a high shape retention property. With such a configuration, the shaped nonwoven fabric of the present invention can have effects of accelerating drying of a liquid and enhancing drying ability of the nonwoven fabric. The shaped nonwoven fabric of the present invention may be formed by laminating two nonwoven fabrics having different specific volumes in one nonwoven fabric. In this case, in a laminated cross section of the shaped nonwoven fabric, a structure having a low specific volume region provided at a center thereof can be made, and a structure having a high specific volume region provided at the center thereof can also be made.

A surface of the nonwoven fabric obtained by the circulation type hot-air dryer of a card method includes a net surface on a transport conveyor side and a net surface on a side opposite thereto (this may hereinafter be referred to as a fuzzy surface in some cases), and the net surface has a relatively low specific volume because the web is pressed against the transport conveyor by circulation air and the fuzzy surface has a relatively high specific volume.

When the shaping processing is performed so that the communicating holes are formed by the upper and lower two-layered nonwoven fabric, in the obtained shaped nonwoven fabric, four types of patterns can be selected in a nonwoven fabric cross section of the portion in which the specific volume of the surface is high depending on which of the net surface and the fuzzy surface described above is up. Of the patterns, FIGS. 5 and 6 show structures of satisfactory combinations particularly for the use of a sanitary material application.

In the shaped nonwoven fabric of the present invention, a surface to be used is not particularly limited, but when it is used as a surface material for sanitary materials such as disposable diapers and sanitary napkins, it is preferable to make the net surface the upper layer because there is a problem of rashes on a surface that touches the skin due to fluff generated by raised hairs of the nonwoven fabric.

EXAMPLES

Hereinafter, the present invention will be described in more detail using examples, but the scope of the present invention is not limited by these examples.

Evaluation of the performance of the shaped nonwoven fabric of the present invention was performed by the following method.

<Method of Evaluating Bulkiness of Nonwoven Fabric>

Using a nonwoven fabric cut into 100 mm×100 mm as a sample, a basis weight of the nonwoven fabric is measured, and a value thereof is defined as A (g/m²).

A thickness of the sample on which the measurement of the basis weight has been performed is measured at four points using Digi-Thickness Tester, and a value of an arithmetic average thereof is defined as B (mm).

A specific volume (nonwoven fabric density) is calculated from these values by the following expression. A higher specific volume indicates more bulkiness.

Specific volume=B/A×1000 (cm³/g)

<Specific Volume Ratio>

A specific volume ratio is calculated from the following expression.

Specific volume ratio=specific volume at portion with low specific volume/specific volume at portion with high specific volume×100 (%)

<Evaluation Method of Absorption Performance>

The absorption performance was determined by putting together (1) evaluation of initial liquid permeability and repeated liquid permeability, and (2) evaluation of liquid returnability.

(1) Evaluation of Initial Liquid Permeability and Repeated Liquid Permeability

On the basis of a method of measuring a liquid passage time of EDANA ERT 150.3-96, liquid permeability was evaluated by measuring a time it took a liquid to pass through a nonwoven fabric sample (a liquid passage time). As a specific method, an absorbent paper ((Kim Towel (trade name) manufactured by CRECIA Co., LTD.) with 4 superimposed layers folded in 4, two sheets) was placed on a holder of an acrylic plate, and a 100 mm×100 mm square nonwoven sample was placed thereon. With it set on the holder, 10 ml of physiological saline was poured using a burette, and the liquid passage time was measured. Also, an aqueous solution in which 9 g of NaCl was completely dissolved in ion-exchanged water to make 1000 g was used for the physiological saline. In regard to a second measurement of the liquid passage time of the same sample, the sample was left as it stood for one minute after completion of the first measurement, thereafter, the sample was sandwiched between 8 sheets each of upper and lower absorbent paper to be subjected to a 35 g/cm² weight and left as it stood for 1 minute, the sample was thereafter subjected to air drying for 3 minutes, and then the second measurement of the liquid passage time was performed. This was repeated three times. When the initial (first) liquid passage time and the liquid passage time of the third repetition were shorter, it indicated more excellent liquid permeability.

(2) Evaluation of Liquid Returnability

Evaluation was performed by a method according to EDANA ERT151.1-96. Also, an absorbent paper that was used was prepared by cutting the Kim towel (trade name) manufactured by CRECIA Co., LTD. into about 90 mm×90 mm (adjusted to be 5.00 to 5.05 g), and 17 ml of the physiological saline measured with a burette was permeated and absorbed. The liquid return amount was evaluated according to the following criteria. When the liquid return amount was smaller, the nonwoven fabric was determined to be more satisfactory.

O: less than 4 g

Δ: 4 g or more and less than 4.5 g

X: 4.5 g or more

<Flexibility Evaluation Method>

Flexibility was evaluated by 10 panelists according to the following criteria.

O: 8 or more people found it flexible.

Δ: 5 or more and 7 or fewer people found it flexible.

X: 4 or fewer people found it flexible.

In the present evaluation method, the nonwoven fabrics rated as 0 or A were rated as having high flexibility.

<Cushioning Property Evaluation Method>

A cushioning property was evaluated by 10 panelists according to the following criteria.

O: 8 or more people found it resilient.

Δ: 5 or more and 7 or fewer people found it resilient.

X: 4 or fewer people found it resilient.

In the present evaluation method, the nonwoven fabrics rated as O or Δ were rated as having a high cushioning property.

In Examples and Comparative Examples of the present invention, the following PE was used as the polyethylene, and the following PET was used as the polyester.

PE: M6900 (trade name) manufactured by Keiyo Polyethylene Co., Ltd.

PET: CZ5022 (trade name) manufactured by Sanfangxiang Industry Co., Ltd.

Sample 1

A nonwoven fabric with a basis weight of 25 g/m² made of sheath-core type composite fibers having a denier of 1.3 dtex in which a sheath component of a sheath/core area ratio 50/50 was PE and a core component thereof was PET was subjected to perforating and shaping processing using a shaping roller (upper and lower temperature of the roller being 120° C.).

The obtained sample 1 had a thickness of 0.73 mm and a specific volume of 29.2 (cm³/g), and a portion with a high specific volume had a ridge that was not thermally compressed.

Sample 2

A nonwoven fabric with a basis weight of 25 g/m² made of sheath-core type composite fibers having a denier of 1.3 dtex in which a sheath component of a sheath/core area ratio 50/50 was PE and a core component thereof was PET was used for an upper layer, a nonwoven fabric with a basis weight of 25 g/m² made of sheath-core type composite fibers having a denier of 2.6 dtex in which a sheath component of a sheath/core area ratio 50/50 was PE and a core component thereof was PET was used for a lower layer, and perforating and shaping processing were performed using a two-layer shaping roller (upper and lower temperature of the roller being 120° C.).

The obtained sample 2 had a thickness of 1.5 mm and a specific volume of 30.6 (cm³/g), and a portion with a high specific volume had a ridge that was not thermally compressed.

Sample 3

For a nonwoven fabric with a basis weight of 25 g/m² made of sheath-core type composite fibers having a denier of 1.3 dtex in which a sheath component of a sheath/core area ratio 50/50 was PE and a core component thereof was PET, perforating and shaping processing were performed using a heat roll (upper and lower temperature of the roll being 115° C.) in which a concavo-convex embossing roll and a pin roll were combined.

The obtained sample 3 had a thickness of 0.35 mm and a specific volume of 14.0 (cm³/g), and a portion with a high specific volume had a ridge that was thermally compressed by the heat roll in which the concavo-convex embossing roll and the pin roll were combined.

Sample 4

A nonwoven fabric with a basis weight of 25 g/m² made of sheath-core type composite fibers having a denier of 1.3 dtex in which a sheath component of a sheath/core area ratio 50/50 was PE and a core component thereof was PET was used for an upper layer, a nonwoven fabric with a basis weight of 25 g/m² made of sheath-core type composite fibers having a denier of 2.6 dtex in which a sheath component of a sheath/core area ratio 50/50 was PE and a core component thereof was PET was used for a lower layer, and shaping processing for the upper layer was performed using a concavo-convex embossing roll (upper and lower temperature of the roll being 80° C.) which was then point-bonded with the lower layer using an ultrasonic bonding machine in order to fix the shaping of the upper layer.

The obtained sample 4 had a thickness of 0.79 mm and a specific volume of 16.7 (cm³/g), and a portion with a high specific volume had a ridge that was thermally compressed by the concavo-convex embossing roll.

Example 1

The sample 1 is a shaped nonwoven fabric having pores and made of a single-layer nonwoven fabric processed using the shaping roller (FIG. 1). It is ascertained that the specific volume is high and it is bulky. Also, the sample 1 was highly rated in the texture evaluation by the 10 panelists, with 8 panelists rating it as having flexibility and 5 panelists rating it as having a high cushioning property.

In regard to the absorption performance, the liquid permeability due to the effect of perforation was high, and the effects in the initial liquid permeability and the repeated liquid permeability were high. Also, in the liquid return, since the shaped convex portion was bulky, the liquid return amount was small. The specific volume ratio was 5.9/29.2×100=20%.

Example 2

The sample 2 is a shaped nonwoven fabric having pores and made of a two-layer nonwoven fabric processed using the shaping roller (FIG. 2). It is ascertained that the specific volume is high and it is bulky. Also, the sample 2 was highly rated in the texture evaluation by the 10 panelists, with 8 panelists rating it as having flexibility and 8 panelists rating it as having a high cushioning property.

In the absorption performance also, the liquid permeability due to the effect of perforation was high, and the effects in the initial liquid permeability and the repeated liquid permeability were high. Also, in the liquid return, since the shaped convex portion was bulky, the liquid return amount was small. The specific volume ratio was 4.9/30.6×100=16%.

Comparative Example 1

The sample 3 is a sample shaped by the concavo-convex embossing roll. The sample 3 tends to be crushed because the convex portion is hollow while the specific volume is high. Also, a shape retention property with respect to tensile stress is poor. In the texture evaluation by the 10 panelists, 4 panelists found it flexible and 4 panelists felt it had a high cushioning property.

As for the absorption performance, although there were effects of the initial liquid permeability and the repeated liquid permeability due to the effect of perforation, since the whole of the nonwoven fabric was consolidated, the liquid return amount was relatively large. The specific volume ratio was 12.6/14.0×100=90%.

Comparative Example 2

The sample 4 is a two-layer nonwoven fabric in which a concavo-convex embossing shaped nonwoven fabric on an upper layer is fixed by a lower layer but tends to be crushed because the convex portion is hollow while the specific volume is high and there is a shape retention property due to the effect of the lower layer. In the texture evaluation by the 10 panelists, 5 panelists found it flexible and 5 panelists felt it had a high cushioning property.

In the absorption performance, the initial liquid permeability, particularly, the repeated liquid permeability, was very low. The specific volume ratio was 14.5/16.7×100=87%.

TABLE 1 Nonwoven fabric Nonwoven fabric (upper layer) Basis (lower layer) Basis Liquid passage time Liquid weight 25 gsm weight 25 gsm (sec) return Resin Denier Resin Denier First Second Third amount Cushioning configuration (dtex) configuration (dtex) time time time (g) Flexibility property Example 1 PE/PET 1.3 — — 0.8 1.0 1.2 3.7 ◯ Δ Example 2 PE/PET 1.3 PE/PET 4.4 0.9 1.2 1.6 3.5 ◯ ◯ Comparative PE/PET 1.3 — — 0.7 0.9 1.4 6.0 X X example 1 Comparative PE/PET 1.3 PE/PET 2.8 1.2 1.5 2.4 4.5 Δ Δ example 2

INDUSTRIAL APPLICABILITY

Because it has the pores, the shaped nonwoven fabric of the present invention can use fibers of a finer denier without the initial liquid permeability and the repeated liquid permeability deteriorating. By using the fibers of fine denier and leaving the thickness of the nonwoven fabric, a shaped nonwoven fabric having flexibility and a high cushioning property can be obtained.

The shaped nonwoven fabric obtained by the present invention can be suitably used for a surface material of sanitary applications.

REFERENCE SIGNS LIST

1 Thermal compression shaping roll

2 Upper thermal roll

3 Lower thermal roll

4 Portion with high specific volume

5 Low specific volume region

6 High specific volume region

7 Portion with high specific volume 

1. A shaped nonwoven fabric in which a portion with a relatively low specific volume and a portion with a relatively high specific volume are linearly present in parallel respectively on a surface of the nonwoven fabric, wherein the portion with a low specific volume alternately includes a thermally compressed part and a porous part, and the portion with a high specific volume includes a ridge that is not thermally compressed.
 2. The shaped nonwoven fabric according to claim 1, wherein, in a nonwoven fabric cross section of the portion with a relatively high specific volume on a surface of the nonwoven fabric, a low specific volume region is provided at a center of the nonwoven fabric cross section.
 3. The shaped nonwoven fabric according to claim 1, wherein, in a nonwoven fabric cross section of the portion with a relatively high specific volume on a surface of the nonwoven fabric, a high specific volume region is provided at a center of the nonwoven fabric cross section.
 4. The shaped nonwoven fabric according to claim 1, wherein a specific volume ratio defined by the following expression is 5% or more and less than 50%. Specific volume ratio=specific volume at portion with low specific volume/specific volume at portion with high specific volume×100 (%) 